Papers by Keyword: Localization

Abstract: A special localization technique is presented for solving steady heat transfer problems, in which the thermal conductivity may depend on space variables. The original problem is split into several subproblems defined on much smaller subdomains. The subproblems are solved using the Method of Fundamental Solutions, which is a truly meshless method. This leads to a Seidel-like iterative technique, which mimics the classical Schwarz overlapping method. The problems associated with large, dense and ill-conditioned matrices are avoided. The method is embedded into a multi-level context, which significantly reduces the computational complexity.

Abstract: The Method of Fundamental Solution applied to the Stokes equation is investigated. Instead of using the classical approach, the problem is split into several subproblems defined on much smaller subdomains. Each local problem is solved by the Method of Fundamental Solutions. Having solved the local problems, the approximate solution is updated at the central point of the local subdomain. This results in a Seidel-like iterative method, which mimics the classical overlapping Schwarz method. In contrast to the traditional Method of Fundamental Solutions, the resulting localized method avoids the problem of large, dense and ill-conditioned linear systems of equations, and, at the same time, remains a truly meshfree technique.

Abstract: Water loss poses a significant problem for water utilities and has received a lot of attention. To fulfill the increasing global demand for water, water supply system operations must be streamlined, making leak detection and location crucial. Water utilities have developed a number of techniques over time for finding leaks in water distribution networks (WDNs). These methodologies range from simple visual inspection to the use of hardware systems and now software using models and algorithms. Data from flow or pressure measurements, which are required for the analysis of water networks, is becoming more readily available with the introduction of intelligent sensor devices. Along with the introduction of geographic information systems (GIS) and supervisory control and data acquisition (SCADA) in the water sector, the deployment of model-driven methodologies for leak detection and localization has found extensive use. This paper aims to provide a concise introductory reference for early researchers in the development of a model-based approach for leak detection in WDNs. Thus, a survey of model-based approaches is presented, along with current research trends and applications of model-driven methodologies for leak detection in water supply networks. Several model-driven approaches and research studies for each case are discussed. Some challenges and research gaps are also discussed.

Abstract: This paper examines the forming of sheet materials by incremental forming. Proposed and researched methods of deformation and the tool path based on which choice is the most appropriate circuits and paths for receiving the hemispherical parts. Abaqus software package is used to develop a method to model incremental forming. All simulation results are analyzed and considered during making conclusion about this forming process.

Abstract: This work aims at investigating the stages and irregularity of plastic strain in austenitic stainless steel 12Kh18N9T within a temperature range of 143 < T < 420 K. The localized plastic strain fronts at different stages of strain hardening have been visualized and monitored via digital speckle photography (DSP). This method consists in the high-accuracy recording of the displacement field via tracking any material surface changes and the subsequent comparison of speckle images acquired under uniaxial tension. The stress-strain diagrams were found to strongly vary with a decrease in temperature due to strain-induced-phase transition. The analysis of localized strain distributions revealed the emergence of a mobile system of equidistant strain localization foci at the strain hardening stage. The temperature dependence of plastic strain localization parameters at the linear strain hardening stage was established as well.

Abstract: It is known that metallic materials are characterized by anisotropy of their mechanical properties, with this being attributed to the conditions during the manufacturing process. For sheet metals, this anisotropy occurs symmetrically to the three orthogonal axes of the rolling, transverse and normal direction. This characteristic is referred to as orthotropic behaviour and manifests itself, for example, in earing during cupping tests. Therefore, orthotropic yield criteria are highly relevant for the numerical simulation of sheet metal forming processes. The Lankford coefficient, also known as the r-value, is a good experimental measure for characterizing orthotropic ductile behaviour of sheets, and can easily aid in parameter identification for yield criteria such as the Hill approaches. In the present investigations, Lankford coefficients were determined as a function of local strain in uniaxial tensile tests through high-resolution digital image correlation. The sample direction was varied between 0°, 45° and 90° to the rolling direction and the test temperature varied from RT to 350 °C at three different strain rates (0.01-1 s^-1). By means of a novel backward analysis, the measuring range for the Lankford coefficients was positioned exactly in the necking area. An increase in temperatures showed a decrease in the initial Lankford coefficient. The results showed non-constant Lankford coefficients and commence the course of a natural exponential function depending on the local strain. Regardless of strain rate, the results revealed that the Lankford coefficients (r-values) at 150 °C, 250 °C and 350 °C approaches a steady-state of r = 1.14 with strains greater than 50 %.

Abstract: Physical theory of reliability is based on research into degradation processes of various origins which take place in a material of a stressed construction. Experimental evaluation of parameters carried out for such processes is a practically important problem by itself. One of the approaches to solving this problem is related to the studies into the stage of material softening due to deformation. This paper analyzes the issues of experimental validation of material softening properties in terms of a phenomenological approach to the problem of structural fracture. Results of deformation analysis for the “machine – model specimen” system, using catastrophe theory are used to form requirements for carrying out experiments which investigate the softening stage of materials. The success of such experiments – which should include recording a branch descending to zero on a computer diagram – is possible when small specimen, made from structurally heterogeneous materials, are strained in a sufficiently rigid testing machine. Thus, the conditions for manifestation of the softening stage connect properties of the material with properties of the load-applying system. Therefore, the material's limiting state – preceding the fractured – also depends on the conditions of loading, and the criteria of that fracture would be nonlocal. In consideration of the results of diagrams plotted from various bases for deformation measurement, a necessity of utilizing local material characteristics for calculation purposes is discussed. As an example of using the complete diagrams for determining kinetics of material degradation from external load, the results of specimen testing, which follows a cyclic training, are cited.

Abstract: In order to investigate the stability and dynamics properties of a cold atom Bose-Einstein Condensate (BEC) in two-dimensional Bessel optical lattices, the stability condition of the system is analyzed and the corresponding Gross-pitaevskii equation (GPE) is solved in this paper by time-dependent variational method and numerical simulation. Firstly, the Euler-Lagrange equation containing the parameters describing the system stability and the effective potential energy needed by the variational analysis method to analyze the system stability is obtained by using the adjustable exponent Gaussian trial wave function. Secondly, according to the analytical solution of Euler-Lagrange equation and the local minimum value of potential energy, the stability condition of the system is further illuminated. Finally, the influence mechanism of these parameters on the local dynamics is revealed by solving the corresponding GPE with numerical method.

Abstract: The article refers to the measures for stage by stage restoration of buildings and structures damaged after both natural and man-made disasters. The work also includes war situations, which according to experts are equivalent to natural disasters. Taking into account the diversity of areas, their geological differences and measures, in each case, localization adjustment is implied. In unpredictable situations such as natural disaster, war operations, restoration of buildings and the organization of tightening works are carried out using the latest methods and technologies. To provide stability of the main frame with strengthening of stone and concrete walls, we suggest strengthening various structures with the method of “sewing of cracks” and using implementation of concrete and asphalt-concrete coatings in the damaged area.

Abstract: A hybrid self-localization system for indoor mobile robot is proposed which is used to get the pose (position and orientation) of the mobile robot within the ultrasonic mesh area while avoiding the drift caused by the odometry system of the robot. This localization system consist of three subsystem-odometry, IMU and ultrasonic mesh. The IMU system is fitted within the robot chassis. The ultrasonic mesh is made by fixing various ultrasonic trans-receivers along two lines parallel to the x-axis at known locations. The IMU system is used to get the heading of the robot and the ultrasonic mesh is used to get the position of the robot, however the odometry system gives both position and orientation of the robot. A simple error threshold based algorithm is used to select the best value of robot pose from the sub-systems.